The present invention relates to a method and an apparatus of recording and reproducing the path of insertion of a cast on dental surveyor.
As it has been well known that there have been several methods disclosed in this dental field for recording the path of insertion of a cast and the reproduction of the tilt on surveyor, such as:
1. Tripod-marks method PA1 2. Vertical lines on sides of base of cast method (scoring method) PA1 3. Three marks on sides of base of cast method PA1 4. Cemented pin method (Ref: 1) PA1 5. Kaloyannides method (Ref: 2) PA1 6. Steas method (Ref: 3)
Among these methods, the vertical lines on sides of a base of cast method (scoring method) has a preferred advantage, i.e., its records can be easily reproduced in any duplication. However, it is not easy to accurately reproduce the tilt of cast on a surveyor, because there are two problems existing in this method. First, the records made on sides of base are done by scoring along a analyzing rod, it may shift to either sides, if there is a space left between the analyzing rod and the cast surface, as shown in FIGS. 1a-1c second, redetermination of the position of the cast on surveyor can be done only by trial and error approach; such procedure is time consuming and the result is not very satisfactory. In the tripod-marks method, it encounters the same problems too.
To make records in the vertical lines on sides of a base cast method (scoring method) accurate, they must be scored perpendicular to the cast surface. In other words, it should be a projection of the analyzing rod on the cast surface. Without other aids, it is difficult to get this job done simply by scoring the cast surface along the edge of the analyzing rod, because there may be a space left between the analyzing rod and the cast surface.
Solution to this problem is, above all, to make the cast surface on which marks are scored trimmed into a flat plane, since it is impossible to scribe a straight line on a curved surface. To aid in making a vertical line, a square block can be used. Making a vertical line, the base of the square block should be in close abutment with the cast surface, one side of it is positioned alonside of the analyzing rod, then the vertical line can be made by scribing along the other side of the block. The records made in this manner will be the projection of the analyzing rod off the cast surface, as shown in FIGS. 2a-2c.
In order to simplify this procedure, a special scoring tool is designed with the same geometric concept.
In general, there are two most common methods for reproducing the original cast position on surveyors given as below:
The scoring method:
Tilting a cast until all three lines marked thereon become again parallel to the analyzing rod, the original cast position can be reestablished. In other words, first, the cast is oriented in adjustment until one line on the base of the cast becomes parallel to the analyzing rod, then it is tried to make the lines on the lateral surfaces of the cast parallel to the analyzing rod. When the east position is altered, all the lines on the cast surfaces will be moved in unison, it is almost impossible to maintain the parallel relationship of the line on the base of the cast with the analyzing rod, having already been established, it will be shifted to either side. By means of a conventional surveyor table equipped with a universal joint, as shown in FIG. 3, an operator can reproduce the tilt of a cast only by trial and error, until all three lines are again parallel to the analyzing rod.
The tripod-mark method:
On returning the cast to the surveyor, it may be tilted until the tip of the analyzing rod again contacts the three dots on the same plane. However, the procedure is not very easy because to make three dots locate on an identical level at one time without trial and error. So, it is necessary to find an easy way to quickly and accurately determine a cast position by way of a new surveyor table.